1. Field of the Invention
The present invention relates to an optical packet exchanger, and more particularly to an optical packet exchanger for switching a transmission path for an optical packet signal by using an address signal.
2. Description of the Related Art
An example of a conventional optical packet exchanger for switching a transmission path for an optical packet signal by using an address signal is a device disclosed in, for example, K. SETO et al., “giga-bit Ethernet textbook”, multimedia tsushin kenkyukai, ASCII corporation, March 1999. FIG. 11 is a block diagram illustrating an exemplary structure of this conventional optical packet exchanger.
In FIG. 11, the conventional optical packet exchanger is composed of an optical transmitter section 1000, an optical transmission section 2000, and a router section 3000. The optical transmitter section 1000 comprises a light source 1001, an optical modulation section 1002, and a data generation section 1003. The router section 3000 comprises an optical splitter section 3001, a photoelectric conversion section 3004, an address extraction section 3005, and a path switching section 3003. The light source 1001 outputs continuous light. The data generation section 1003 generates a data signal, which includes an information signal to be transmitted plus a header, the header being an address signal corresponding to a transmission destination of the information signal. The optical modulation section 1002 subjects the continuous light which is output from the light source 1001 to an intensity modulation, using the data signal generated by the data generation section 1003. The optical splitter section 3001 splits an optical packet, which is input via the optical transmission section 2000, into two. The photoelectric conversion section 3004 converts one of the output optical packets from the optical splitter section 3001 into an electrical signal. As a result of this process, the data signal is taken out of the optical packet. The address extraction section 3005 removes the information signal from the data signal which has been taken out by the photoelectric conversion section 3004. As a result of this process, the address signal is extracted. In accordance with the address signal which has been extracted by the address extraction section 3005, the path switching section 3003 determines the path for the other output optical packet from the optical splitter section 3001.
However, the aforementioned conventional optical packet exchanger has a problem in that, since a data signal to which the address signal corresponding to the information signal is added as a header is used, the transmittable capacity is decreased by the amount corresponding to the address signal; that is, the transmission efficiency is decreased. In addition, when the modulation speed for the information signal becomes high, the modulation speed for the address signal also becomes high. This makes it difficult for the address extraction section 3005 in the router section 3000 to read the address signal.
Therefore, an object of the present invention is to provide an optical packet exchanger which, in a situation where a transmission path for an optical packet is to be switched by using an address signal, prevents the transmittable capacity for the information signal from being decreased due to the increased transmission size ascribable to the address signal, and which facilitates the extraction of the address signal even if the modulation speed for the information signal becomes high.